public class Solution {
    public boolean hasCycle(ListNode head) {
        if(head ==null ||head.next==null) {
            return false;
        }
        ListNode fast = head.next;
        ListNode slow = head;
        while(fast!=slow) {
            if(fast==null || fast.next==null) {
                return false;
            }
            fast=fast.next.next;
            slow=slow.next;
        }
        return true;
    }
}
public class lc141 {
}
